Why Do Some Still Blame Vaccines for Autism?

February 25, 2009 - Here’s a question: How do you decide what to think about a controversial issue? Must you become an expert on the issue? Must you devote thousands upon thousands of hours to poring over the evidence, checking and rechecking every fact through firsthand research and experimentation? Clearly, this is impossible even for an expert, who must accept a whole slew of facts as given. And just as clearly, an expert is an expert in only one area. What about all of the other controversies?

One option is merely to refrain from deciding. Sometimes this is perfectly feasible. But in the case of the purported link between childhood vaccines and autism, which was recently in the news again, sitting on the fence is not an option. At least for parents of young children, it is of the utmost importance to decide whether or not to vaccinate. Indeed, it is quite literally a matter of life and death. Vaccines prevent serious illnesses and save lives. But do they also cause autism?

A Verdict for Vaccines

Eleven years ago, in February 1998, Dr. Andrew Wakefield held a press conference that was to set off a furious debate. Wakefield announced a study that he and 12 of his colleagues were publishing in the respected medical journal The Lancet. The results of that study: a possible link between childhood vaccines and autism. Jump ahead to this past February 12, 2009—coincidentally the 200^th anniversary of the birth of Charles Darwin, a towering scientific figure who is himself the subject of continuing controversy. On that day, two weeks ago, the U.S. “ Vaccine Court ” (officially, the Office of Special Masters of the U.S. Court of Federal Claims) essentially concluded, in three separate test cases, that vaccines do not cause autism.

Who to believe? Do we simply accept the decisions of the three judges of the court? With so much at stake, we need not be quite so passive. It is true that most of us have neither the time nor the ability to sift through the 5,000 pages of expert testimony and 939 scientific articles upon which the judges based their decisions. But we can instead do our best to examine the overall form of the arguments being made by both sides in this controversy. We can see which side is following the rules of logic, and which side is breaking them. And we can see which side the evidence favors, and which side is ignoring any contradictory evidence and spinning conspiracy theories to explain why the “truth” is not being told.

All of which is easier said than done. Critical thinking does not just happen automatically, and we must be careful to avoid logical errors ourselves. The most pernicious logical fallacy may be confirmation bias, which is to say, seeking out and prioritizing confirmation of our preexisting beliefs instead of testing those beliefs by really examining both sides in a controversy. Thinking logically takes some effort, but it is a skill like any other, a skill that can be learned—and a vitally important one at that.

How to Think Straight

One logical fallacy that is prominently on display in the vaccine-autism controversy is post hoc ergo propter hoc (roughly “after this therefore because of this”). This is a fallacy because the bare fact of one thing following another is no proof that the second thing was caused by the first. The sequence may turn out to have been a pure coincidence that is not borne out by subsequent statistical studies. (Indeed, even a solid statistical correlation is not proof of causation, since correlated variables may share some other cause.) Because symptoms of autism tend to manifest at around the age when children get vaccinated, it is inevitable that in some cases, the one will just coincidentally follow closely behind the other even if it turns out that statistical research finds no correlation whatsoever among children generally. Anecdotal evidence is therefore particularly unreliable here. Anecdotes may suggest a line of inquiry worth pursuing, but scientific tests with rigorous controls are necessary to tease out the truth.

A little bit of Internet sleuthing quickly provided me with an example of an autism-vaccine activist engaged in post hoc thinking. In the wake of the court’s recent decisions, Barbara Fischkin, a self-described Autism Mom, wrote that “the connection between autism and vaccines has been spotted by multitudes of front line participants and observers—parents and physicians who have seen children and patients fall apart after being vaccinated.” (Emphasis added.) Fischkin goes on to bemoan the fact that these “eyewitness accounts” have been ignored.

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The anecdotal evidence linking vaccines to autism has been tested over and over again, and it has been found wanting.

But has this anecdotal evidence really been ignored? Not at all. In fact, it has been tested over and over again, and it has been found wanting. An in-depth Newsweek article from the most recent issue of the magazine (dated March 2, 2009) supplies a good deal of background. It outlines Dr. Wakefield’s initial study, as well as other subsequent studies that seemed to support the autism-vaccine link. Then it describes further studies, some involving millions of children, failing to establish the link suggested by the far smaller earlier studies. It also informs us that 10 of Wakefield’s original 12 co-authors have since retracted their paper’s suggestion of a vaccine-autism link.

This leads us nicely to another logical issue in this controversy: the burden of proof. Fischkin, for example, argues that these most recent court decisions do not mean the case is closed, because last year, the court “ruled that, in effect vaccines could cause autism.” (Emphasis in original.) Maybe so, but to say a thing is possible is not to say that it exists. The burden of proof here is not on the side denying the existence of a link. The burden of proof is on the side claiming that there is a link despite repeated failure to establish one.

The Problem with Conspiracy Theories

Losing the battle of logic and evidence, autism-vaccine crusaders sink to impugning the motives of their many opponents, an example of the ad hominem fallacy. The government, they say, is complicit in a cover up. So are the media, who initially fanned the flames of this controversy but have since doused them. The worst offender, of course, is the pharmaceutical industry, which according to a California pediatrician quoted by Fischkin, “controls which research gets into journals and which does not.” The root of all this evil? You guessed it: money.

Well, if we’re going to play another round of Follow the Money instead of talking about actual evidence and arguments, let’s at least remember that both sides in this controversy have pecuniary interests. The plaintiffs at the Vaccine Court are seeking monetary damages, after all. And Dr. Wakefield is himself facing charges of professional misconduct for, among other things, a financial conflict of interest in connection with his initial study. The point is not that plaintiffs seeking damages are necessarily corrupt, but that if we’re going to play this game, we need to admit that both sides in this controversy have a vested interest in the outcome. An interest in money does not prove dishonesty, but if it did, both sides would be convicted, along with most of the human race.

The problem with conspiracy theories is that they only remain plausible as long as they remain divorced from any larger context. To attack just one more of the shaky pillars supporting this particular house of cards: If pharmaceutical companies were really controlling what gets published in medical journals, it would be the story of the century, and some intrepid journalist would win herself a Pulitzer exposing it. They don’t give Pulitzers for unsubstantiated allegations, though.

Eleven years ago, there was some reason for a person following the news to fear that vaccines might play a role in causing autism. Today, the evidence and arguments strongly suggest that this is not the case. Vaccines are a boon to humanity, and a shining example of humanity’s creative genius for solving problems. They are not risk-free, but the benefits far outweigh the risks, and as far as we can tell, autism is not one of the risks. It is my considered opinion that the conspiracy theorists in this case are stretching the bounds of plausibility to the breaking point. But please do not take my word for it. Read the Fischkin and Newsweek articles, and others as well. Especially if you have a small child, pick up a book or two arguing each side of this controversy and read them with a critical mind. For this relatively small investment of time and energy, you just might save your child’s life.

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